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                                                                    Exhibit 31.1

                            CERTIFICATION PURSUANT TO
               RULE 13a-14 OF THE SECURITIES EXCHANGE ACT OF 1934,
                             AS ADOPTED PURSUANT TO
                  SECTION 302 OF THE SARBANES-OXLEY ACT OF 2002

I, Peter K. Hansen, certify that:

1.    I have reviewed this quarterly report on Form 10-Q of NYFIX, Inc.;

2.    Based on my knowledge,  this report does not contain any untrue  statement
      of a material fact or omit to state a material fact  necessary to make the
      statements made, in light of the circumstances under which such statements
      were made,  not  misleading  with  respect  to the period  covered by this
      report;

3.    Based on my  knowledge,  the  financial  statements,  and other  financial
      information  included  in this  report,  fairly  present  in all  material
      respects the financial condition,  results of operations and cash flows of
      the registrant as of, and for, the periods presented in this report;

4.    The  registrant's  other  certifying  officer  and I are  responsible  for
      establishing  and  maintaining  disclosure  controls  and  procedures  (as
      defined in Exchange Act Rules  13a-15(e) and 15d-15(e)) for the registrant
      and have:

      a.   Designed  such  disclosure  controls and  procedures,  or caused such
           disclosure   controls  and   procedures  to  be  designed  under  our
           supervision,  to ensure  that  material  information  relating to the
           registrant, including its consolidated subsidiaries, is made known to
           us by others within those entities, particularly during the period in
           which this report is being prepared;

      b.   Evaluated the effectiveness of the registrant's  disclosure  controls
           and procedures and presented in this report our conclusions about the
           effectiveness  of the disclosure  controls and procedures,  as of the
           end of the period  covered by this report  based on such  evaluation;
           and

      c.   Disclosed  in this  report  any change in the  registrant's  internal
           control  over   financial   reporting   that   occurred   during  the
           registrant's  most recent  fiscal  quarter (the  registrant's  fourth
           fiscal  quarter in the case of an annual  report) that has materially
           affected,   or  is  reasonably  likely  to  materially   affect,  the
           registrant's internal control over financial reporting; and

5.    The registrant's other certifying  officer and I have disclosed,  based on
      our most recent  evaluation of internal control over financial  reporting,
      to the  registrant's  auditors and the audit committee of the registrant's
      board of directors (or persons performing the equivalent functions):

      a.   All significant deficiencies and material weaknesses in the design or
           operation of internal  control  over  financial  reporting  which are
           reasonably  likely to adversely  affect the  registrant's  ability to
           record, process, summarize and report financial information; and

      b.   Any fraud, whether or not material, that involves management or other
           employees who have a significant  role in the  registrant's  internal
           control over financial reporting.

Date: August 9, 2004

Peter K. Hansen
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Peter K. Hansen
Chairman, President and
Chief Executive Officer
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